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Home arrow Nutrition arrow Intermittent Fasting arrow 24-Hour Fast: What Is It, and How Does It Work?

24-Hour Fast: What Is It, and How Does It Work?

Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: October 17, 2023
9 min read 1343 Views 0 Comments
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Not eating for a certain amount of time is supposed to promote weight loss. This includes fasting for 24 hours, which might be challenging for beginners. We explain what the 24-hour fast is, how it works, and the potential key benefits of following this specific fast.

24 hour fast

Fasting has been a popular way to lose stored fats.

There are lots of methods you can try, one being the 24-hour fast. Not eating for a whole day might sound challenging, but it could progress your weight loss journey. 

More advanced fasters might try this specific eating schedule when burning excess fat. Beginners can still attempt the challenge, as testing personal boundaries will encourage determination. You might be wondering – how does this fast work, and what are the benefits?

In this article, you’ll discover what the 24-hour fast is and how to start. 

24-Hour Fast – What Is It?

The 24-hour fast means you can’t consume calories for 24 hours. Not eating for a whole day is supposed to promote weight loss by pushing your body into ketosis. During this time, you can only have zero-calorie beverages that won’t break your current fast.

You can choose what time you want to start and end the long fast. Some people stop eating their dinner at 7 PM one evening and eat again at 7 PM the next day. It depends on your daily schedule, weight goals, and whether you want to break your 24-hour fast with a big meal.

Fasting for 24 hours should only be attempted 1–2 times a week. This is to ensure you don’t starve your body and experience nutritional deficiencies in your diet. For example, you might do the 24-hour fast on a Monday and then try it again on Friday to lose some stubborn weight.

Can You Lose Weight by Not Eating for 24 Hours?

You can lose weight, but that will only be lost water weight and not fat. The body begins to drop a few pounds when you stay consistent with exercise and dieting. Since you’ll mainly lose water and salt, the stomach may look more toned after 24 hours. 

People shouldn’t do the 24-hour fast if they want rapid weight loss results. This fast only reduces bloating and removes toxins that could accelerate fat production. After eight hours of not eating, the body will use fat stores for energy, but that won’t show much physical change. 

However, repeating this fasting method once or twice a week could encourage long-term weight loss. Cutting down on food may strengthen the metabolism, as it doesn’t need to break down lots of glucose. A fast metabolism means your body will burn extra calories during the day.

How to Fast for a Day?

To fast for 24 hours, you need to prepare your body. Drink at least 8 cups of water, eat small, nutrient-dense meals, and get plenty of sleep before the fast. This preparation should stop you from feeling hungry and exhausted when fasting for the whole day.

Going straight into the 24-hour fast can be dangerous. If you haven’t eaten full meals, the body will become hungry quickly and make you feel sick. This isn’t something you want to experience for 24 hours straight, so always take preparations seriously when trying intermittent fasting. 

People usually drink lots of water to stay hydrated before the fast. Water is necessary to flush out fat cells from the body, encouraging further weight loss. You can also drink this beverage during the 24-hour fast to keep your stomach full and prevent those horrible hunger pangs

Health Benefits of Fasting for 24 Hours

There are many benefits that derive from intermittent fasting. Losing weight might be the main goal, but there are other advantages to not eating for 24 hours. Your body goes through many changes that you don’t see, so it’s important to learn about the long-term physical effects.

Let’s take a look at the 6 potential health benefits of 24-hour fasting: 

#1 Better blood sugar levels

Fasting for 24 hours can help reduce blood glucose levels. This is great for people who have type 2 diabetes and need to monitor their health. Since you’re not eating throughout the whole day, your body can’t produce excess insulin that will eventually raise blood sugar content. 

Not regulating your blood sugar could damage blood vessels and important organs. You’ll be more at risk of developing cardiovascular diseases in the long term. To get low blood sugar levels, eat balanced meals during your eating window and fast for 24 hours once a week. 

#2 Might help to prevent cancer

Once you’re in the fasting state, autophagy will happen during this time. Autophagy is a natural process that helps your body clean out damaged cells. These cells might be cancerous, meaning intermittent fasting can prevent cancer by removing them during autophagy.

Some people also try fasting when undergoing cancer treatments. Not eating for certain periods may reduce chemotherapy-related toxicity and possible brain tumors. However, you should consult with your doctor before doing this, as avoiding food might not be good for recovery.

#3 Improves cognitive function

Just after six hours of consistent fasting, your body releases more of the human growth hormone (HGH). This hormone can strengthen brain cells and improve cognitive function. A 24-hour fast, when done correctly, could also prevent memory loss in those who are aging. 

Autophagy may eliminate damaged cells that increase the risk of Parkinson’s disease. This is because free radicals target healthy brain cells and trigger oxidative stress. If you struggle with concentration problems, try fasting for 24 hours to notice the difference in your focus.

#4 Promotes heart health

Completing the 24-hour fast could lower high blood pressure. Intermittent fasting encourages people to cut out junk food from their diet, which prevents plaque buildup in the arteries. Low blood pressure reduces the risk of heart disease, kidney disease, and metabolic syndrome. 

Another great benefit is that fasting decreases low-density lipoprotein – bad cholesterol in your body. Too much LDL cholesterol can restrict blood flow and cause blood pressure spikes. The good kind of lipids build healthy cells and remove bad fats traveling in the bloodstream.

People who lose body fat while fasting may also have better heart health. The body burns fat during the fasting period, preventing diabetes or obesity. Of course, in the long term, your heart grows stronger without facing the risk of cardiovascular diseases and excess blood triglycerides.

#5 Enhances metabolic rate

Short-term fasting can boost your metabolic rate by 14%. This is great for people who have a slow metabolism and don’t burn enough calories throughout the day. Fasting increases the hormone norepinephrine, which promotes fat-burning and maintains strong muscle mass.

People with a fast metabolism usually experience fat loss quickly. Their bodies need more energy to function properly when losing weight. However, if you want to experience the same metabolic rate, always maintain a good calorie intake outside of the fasting window.

Not eating enough food before and after the 24-hour fast could slow the metabolism. This means you’ll gain weight when eating less. It might be tempting to starve your body even more after the fast, but it still needs plenty of energy to boost the fat-burning mechanisms.

#6 Weight loss

The main reason you might be fasting is to reduce your body weight. Fasting is one healthy way to lose stubborn fat and reach your weight loss goals. Doing the 24-hour fast once a week can encourage the body to enter ketosis – a metabolic state that burns fat and not glucose stores.

One study found that people lost 4–16% of their body fat over the course of 3–12 weeks. How much weight you lose in a month can depend on calorie restriction, exercise plan, and metabolic rate. For example, someone who eats 500 fewer calories is more likely to lose that weight.

Intermittent fasting for 24 hours could also retain muscle tissue. People who try this method often have more muscle that burns through extra calories. The only way you won’t lose some muscle is by following a strict calorie deficit, so always eat nutrient-dense foods in your diet.

Just remember that fasting alone won’t significantly cause weight loss. You need to do exercise and create healthy lifestyle habits. For example, a long-distance run every morning could burn more calories. Cardio-based exercise is key to reducing your overall body weight percentage.

Side Effects of a 24-Hour Fast

Fasting for 24 hours is bound to come with some side effects. Not everyone will experience the same physical changes, but it’s important to stay aware of any symptoms. You should consult with your doctor if you don’t feel well or need medical supervision before starting the schedule.

One common side effect is getting frequent headaches. This is because of electrolyte imbalances, dehydration, and low blood glucose levels. You can overcome this physical challenge by drinking lots of water and eating nutrient-dense foods before the fast. 

Another feeling you might get is fatigue throughout the day. The human body craves food, so taking that energy source away can leave you feeling exhausted. Fatigue isn’t something to be worried about, as you’ll soon gain the energy back after completing the 24-hour fast.

Hunger pangs while fasting can be challenging for beginners. Your digestive system screams for food, but you can’t have any until the 24 hours are finished. To avoid this uncomfortable side effect, stay hydrated and have other zero-calorie beverages like plain tea and black coffee.

People who have sensitive stomachs might experience problems with their digestive system. This could be diarrhea, nausea, bloating, and serious constipation. The sudden calorie restriction might reduce the water content in your intestines, further disrupting digestive function. Therefore, it is better to start slow or try different methods, such as fat fast.

How to Break a 24-Hour Fast

Breaking a fast is very important for relaxing the digestive system. You can’t go straight into big meals that could trigger abdominal pain. Even though it might be tempting to raid your food stock after 24 hours, try to make a small meal that is full of dietary fiber, protein, and vitamins.

Some people drink lots of water while breaking their fast. This can lubricate your stomach and help prepare it for digestion after meals. You can also have a fruit smoothie that contains leafy greens and berries, as these are great for preventing sickness and weakness after fasting.

The best food to break a fast includes whole eggs, bone broth, chia seeds, fermented foods, and dried fruits. These don’t require lots of digestion, especially if your stomach is adjusting after the fasting window. Just make sure to get healthy fats when going back to your diet.

Not breaking the fast slowly could trigger health complications. This might be constipation and severe stomach pain, as your body can’t digest the food properly. You may not experience the same health benefits when rushing the process of both autophagy and ketosis.

A Word From Our MD

Fasting for 24 hours can help you lose stubborn weight, but it might not be good for everyone on their weight loss journey. Those who have experienced past eating disorders should avoid this method, as you don’t want to build an unhealthy relationship with eating healthy meals.

Pregnant or breastfeeding women should also stay clear of intermittent fasting. The body needs time to develop and produce milk for the baby. If you do want to achieve weight loss after giving birth, consult with your doctor about the best ways to lose weight slowly and safely.

Intermittent fasting has many health benefits that improve natural functions in the body. For those who don’t want to fast for 24 hours, try alternate-day fasting or normal time-restricted eating. It’s better to start off easy than jump head first into a new daily eating schedule.

If you currently have any health conditions, speak to your doctor before trying this fast. A medical professional can advise the recommended caloric intake. They might also refer you to a registered dietitian who can talk about the right fasting diet for your long-term health.


So, are the health benefits worth fasting for 24 hours?

You should definitely try this type of fast when losing stubborn weight. It’s great for improving blood sugar control, your immune system, and even inflammation from chronic conditions. All the benefits ensure the body starts burning fat and getting you to your ideal weight.

Just make sure to eat lots of nutrient-dense foods before and after the fast. You don’t want your daily calorie restriction to be too strict. If you’re taking medication, have a history of eating disorders, or are currently pregnant, consult with your doctor before intermittent fasting.

Written by Edibel Quintero, RD
Edibel Quintero is a medical doctor who graduated in 2013 from the University of Zulia and has been working in her profession since then. She specializes in obesity and nutrition, physical rehabilitation, sports massage and post-operative rehabilitation. Edibel’s goal is to help people live healthier lives by educating them about food, exercise, mental wellness and other lifestyle choices that can improve their quality of life.
The article was fact checked by Rosmy Barrios, MD
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Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: October 17, 2023
9 min read 1343 Views 0 Comments

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